2 ## Copyright (c) 2000-2004, Index Data.
4 ## Permission to use, copy, modify, distribute, and sell this software and
5 ## its documentation, in whole or in part, for any purpose, is hereby granted,
8 ## 1. This copyright and permission notice appear in all copies of the
9 ## software and its documentation. Notices of copyright or attribution
10 ## which appear at the beginning of any file must remain unchanged.
12 ## 2. The name of Index Data or the individual authors may not be used to
13 ## endorse or promote products derived from this software without specific
14 ## prior written permission.
16 ## THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND,
17 ## EXPRESS, IMPLIED, OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
18 ## WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
19 ## IN NO EVENT SHALL INDEX DATA BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
20 ## INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES
21 ## WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR
22 ## NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
23 ## LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
28 ## $Id: SimpleServer.pm,v 1.25 2006-04-19 12:38:49 mike Exp $
30 package Net::Z3950::SimpleServer;
33 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);
40 @ISA = qw(Exporter AutoLoader DynaLoader);
44 bootstrap Net::Z3950::SimpleServer $VERSION;
46 # Preloaded methods go here.
56 carp "SimpleServer.pm: WARNING: Multithreaded server unsupported";
60 croak "SimpleServer.pm: ERROR: Unspecified search handler" unless defined($self->{SEARCH});
61 croak "SimpleServer.pm: ERROR: Unspecified fetch handler" unless defined($self->{FETCH});
72 if (defined($self->{INIT})) {
73 set_init_handler($self->{INIT});
75 set_search_handler($self->{SEARCH});
76 set_fetch_handler($self->{FETCH});
77 if (defined($self->{CLOSE})) {
78 set_close_handler($self->{CLOSE});
80 if (defined($self->{PRESENT})) {
81 set_present_handler($self->{PRESENT});
83 if (defined($self->{SCAN})) {
84 set_scan_handler($self->{SCAN});
91 # Register packages that we will use in translated RPNs
92 package Net::Z3950::APDU::Query;
93 package Net::Z3950::APDU::OID;
94 package Net::Z3950::RPN::And;
95 package Net::Z3950::RPN::Or;
96 package Net::Z3950::RPN::AndNot;
97 package Net::Z3950::RPN::Term;
98 package Net::Z3950::RPN::RSID;
99 package Net::Z3950::RPN::Attributes;
100 package Net::Z3950::RPN::Attribute;
102 # Must revert to original package for Autoloader's benefit
103 package Net::Z3950::SimpleServer;
106 # Autoload methods go after =cut, and are processed by the autosplit program.
110 # Below is the stub of documentation for your module. You better edit it!
114 Net::Z3950::SimpleServer - Simple Perl API for building Z39.50 servers.
118 use Net::Z3950::SimpleServer;
120 sub my_search_handler {
123 my $set_id = $args->{SETNAME};
124 my @database_list = @{ $args->{DATABASES} };
125 my $query = $args->{QUERY};
127 ## Perform the query on the specified set of databases
128 ## and return the number of hits:
130 $args->{HITS} = $hits;
133 sub my_fetch_handler { # Get a record for the user
136 my $set_id = $args->{SETNAME};
138 my $record = fetch_a_record($args->{OFFSET});
140 $args->{RECORD} = $record;
141 if (number_of_hits() == $args->{OFFSET}) { ## Last record in set?
149 ## Register custom event handlers:
151 my $z = new Net::Z3950::SimpleServer( INIT => \&my_init_handler,
152 CLOSE => \&my_close_handler,
153 SEARCH => \&my_search_handler,
154 FETCH => \&my_fetch_handler);
157 $z->launch_server("ztest.pl", @ARGV);
161 The SimpleServer module is a tool for constructing Z39.50 "Information
162 Retrieval" servers in Perl. The module is easy to use, but it
163 does help to have an understanding of the Z39.50 query
164 structure and the construction of structured retrieval records.
166 Z39.50 is a network protocol for searching remote databases and
167 retrieving the results in the form of structured "records". It is widely
168 used in libraries around the world, as well as in the US Federal Government.
169 In addition, it is generally useful whenever you wish to integrate a number
170 of different database systems around a shared, asbtract data model.
172 The model of the module is simple: It implements a "generic" Z39.50
173 server, which invokes callback functions supplied by you to search
174 for content in your database. You can use any tools available in
175 Perl to supply the content, including modules like DBI and
178 The server will take care of managing the network connections for
179 you, and it will spawn a new process (or thread, in some
180 environments) whenever a new connection is received.
182 The programmer can specify subroutines to take care of the following type
188 - Fetching of records
189 - Scan request (browsing)
190 - Closing down connection
192 Note that only the Search and Fetch handler functions are required.
193 The module can supply default responses to the other on its own.
195 After the launching of the server, all control is given away from
196 the Perl script to the server. The server calls the registered
197 subroutines to field incoming requests from Z39.50 clients.
199 A reference to an anonymous hash is passed to each handler. Some of
200 the entries of these hashes are to be considered input and others
203 The Perl programmer specifies the event handlers for the server by
204 means of the SimpleServer object constructor
206 my $z = new Net::Z3950::SimpleServer(
207 INIT => \&my_init_handler,
208 CLOSE => \&my_close_handler,
209 SEARCH => \&my_search_handler,
210 PRESENT => \&my_present_handler,
211 SCAN => \&my_scan_handler,
212 FETCH => \&my_fetch_handler);
214 If you want your SimpleServer to start a thread (threaded mode) to
215 handle each incoming Z39.50 request instead of forking a process
216 (forking mode), you need to register the handlers by symbol rather
217 than by code reference. Thus, in threaded mode, you will need to
218 register your handlers this way:
220 my $z = new Net::Z3950::SimpleServer(
221 INIT => "my_package::my_init_handler",
222 CLOSE => "my_package::my_close_handler",
226 where my_package is the Perl package in which your handler is
229 After the custom event handlers are declared, the server is launched
230 by means of the method
232 $z->launch_server("MyServer.pl", @ARGV);
234 Notice, the first argument should be the name of your server
235 script (for logging purposes), while the rest of the arguments
236 are documented in the YAZ toolkit manual: The section on
237 application invocation: <http://www.indexdata.dk/yaz/yaz-7.php>
239 In particular, you need to use the -T switch to start your SimpleServer
244 The init handler is called whenever a Z39.50 client is attempting
245 to logon to the server. The exchange of parameters between the
246 server and the handler is carried out via an anonymous hash reached
251 The argument hash passed to the init handler has the form
254 ## Response parameters:
256 IMP_ID => "", ## Z39.50 Implementation ID
257 IMP_NAME => "", ## Z39.50 Implementation name
258 IMP_VER => "", ## Z39.50 Implementation version
259 ERR_CODE => 0, ## Error code, cnf. Z39.50 manual
260 ERR_STR => "", ## Error string (additional info.)
261 USER => "xxx" ## If Z39.50 authentication is used,
262 ## this member contains user name
263 PASS => "yyy" ## Under same conditions, this member
264 ## contains the password in clear text
265 HANDLE => undef ## Handler of Perl data structure
268 The HANDLE member can be used to store any scalar value which will then
269 be provided as input to all subsequent calls (ie. for searching, record
270 retrieval, etc.). A common use of the handle is to store a reference to
271 a hash which may then be used to store session-specific parameters.
272 If you have any session-specific information (such as a list of
273 result sets or a handle to a back-end search engine of some sort),
274 it is always best to store them in a private session structure -
275 rather than leaving them in global variables in your script.
277 The Implementation ID, name and version are only really used by Z39.50
278 client developers to see what kind of server they're dealing with.
279 Filling these in is optional.
281 The ERR_CODE should be left at 0 (the default value) if you wish to
282 accept the connection. Any other value is interpreted as a failure
283 and the client will be shown the door, with the code and the
284 associated additional information, ERR_STR returned.
286 =head2 Search handler
288 Similarly, the search handler is called with a reference to an anony-
289 mous hash. The structure is the following:
292 ## Request parameters:
294 HANDLE => ref, ## Your session reference.
295 SETNAME => "id", ## ID of the result set
296 REPL_SET => 0, ## Replace set if already existing?
297 DATABASES => ["xxx"], ## Reference to a list of data-
299 QUERY => "query", ## The query expression
300 RPN => $obj, ## Reference to a Net::Z3950::APDU::Query
302 ## Response parameters:
304 ERR_CODE => 0, ## Error code (0=Succesful search)
305 ERR_STR => "", ## Error string
306 HITS => 0 ## Number of matches
309 Note that a search which finds 0 hits is considered successful in
310 Z39.50 terms - you should only set the ERR_CODE to a non-zero value
311 if there was a problem processing the request. The Z39.50 standard
312 provides a comprehensive list of standard diagnostic codes, and you
313 should use these whenever possible.
315 The QUERY is a tree-structure of terms combined by operators, the
316 terms being qualified by lists of attributes. The query is presented
317 to the search function in the Prefix Query Format (PQF) which is
318 used in many applications based on the YAZ toolkit. The full grammar
319 is described in the YAZ manual.
321 The following are all examples of valid queries in the PQF.
327 @or "dylan" "zimmerman"
331 @or @and bob dylan @set Result-1
333 @and @attr 1=1 "bob dylan" @attr 1=4 "slow train coming"
335 @attrset @attr 4=1 @attr 1=4 "self portrait"
337 You will need to write a recursive function or something similar to
338 parse incoming query expressions, and this is usually where a lot of
339 the work in writing a database-backend happens. Fortunately, you don't
340 need to support anymore functionality than you want to. For instance,
341 it is perfectly legal to not accept boolean operators, but you SHOULD
342 try to return good error codes if you run into something you can't or
345 A more convenient alternative to the QUERY member may be the RPN
346 member, which is a reference to a Net::Z3950::APDU::Query object
347 representing the RPN query tree. The structure of that object is
348 supposed to be self-documenting, but here's a brief summary of what
355 C<Net::Z3950::APDU::Query> is a hash with two fields:
361 =item C<attributeSet>
363 Optional. If present, it is a reference to a
364 C<Net::Z3950::APDU::OID>. This is a string of dot-separated integers
365 representing the OID of the query's top-level attribute set.
369 Mandatory: a refererence to the RPN tree itself.
375 Each node of the tree is an object of one of the following types:
381 =item C<Net::Z3950::RPN::And>
383 =item C<Net::Z3950::RPN::Or>
385 =item C<Net::Z3950::RPN::AndNot>
387 These three classes are all arrays of two elements, each of which is a
388 node of one of the above types.
390 =item C<Net::Z3950::RPN::Term>
392 See below for details.
394 =item C<Net::Z3950::RPN::RSID>
396 A reference to a result-set ID indicating a previous search. The ID
397 of the result-set is in the C<id> element.
401 (I guess I should make a superclass C<Net::Z3950::RPN::Node> and make
402 all of these subclasses of it. Not done that yet, but will do one day.)
410 C<Net::Z3950::RPN::Term> is a hash with two fields:
418 A string containing the search term itself.
422 A reference to a C<Net::Z3950::RPN::Attributes> object.
428 C<Net::Z3950::RPN::Attributes> is an array of references to
429 C<Net::Z3950::RPN::Attribute> objects. (Note the plural/singular
434 C<Net::Z3950::RPN::Attribute> is a hash with three elements:
440 =item C<attributeSet>
442 Optional. If present, it is dot-separated OID string, as above.
444 =item C<attributeType>
446 An integer indicating the type of the attribute - for example, under
447 the BIB-1 attribute set, type 1 indicates a ``use'' attribute, type 2
448 a ``relation'' attribute, etc.
450 =item C<attributeValue>
452 An integer indicating the value of the attribute - for example, under
453 BIB-1, if the attribute type is 1, then value 4 indictates a title
454 search and 7 indictates an ISBN search; but if the attribute type is
455 2, then value 4 indicates a ``greater than or equal'' search, and 102
456 indicates a relevance match.
462 Note that, at the moment, none of these classes have any methods at
463 all: the blessing into classes is largely just a documentation thing
464 so that, for example, if you do
466 { use Data::Dumper; print Dumper($args->{RPN}) }
468 you get something fairly human-readable. But of course, the type
469 distinction between the three different kinds of boolean node is
472 By adding your own methods to these classes (building what I call
473 ``augmented classes''), you can easily build code that walks the tree
474 of the incoming RPN. Take a look at C<samples/render-search.pl> for a
475 sample implementation of such an augmented classes technique.
478 =head2 Present handler
480 The presence of a present handler in a SimpleServer front-end is optional.
481 Each time a client wishes to retrieve records, the present service is
482 called. The present service allows the origin to request a certain number
483 of records retrieved from a given result set.
484 When the present handler is called, the front-end server should prepare a
485 result set for fetching. In practice, this means to get access to the
486 data from the backend database and store the data in a temporary fashion
487 for fast and efficient fetching. The present handler does *not* fetch
488 anything. This task is taken care of by the fetch handler, which will be
489 called the correct number of times by the YAZ library. More about this
491 If no present handler is implemented in the front-end, the YAZ toolkit
492 will take care of a minimum of preparations itself. This default present
493 handler is sufficient in many situations, where only a small amount of
494 records are expected to be retrieved. If on the other hand, large result
495 sets are likely to occur, the implementation of a reasonable present
496 handler can gain performance significantly.
498 The informations exchanged between client and present handle are:
501 ## Client/server request:
503 HANDLE => ref, ## Reference to datastructure
504 SETNAME => "id", ## Result set ID
505 START => xxx, ## Start position
506 COMP => "", ## Desired record composition
507 NUMBER => yyy, ## Number of requested records
510 ## Respons parameters:
512 HITS => zzz, ## Number of returned records
513 ERR_CODE => 0, ## Error code
514 ERR_STR => "" ## Error message
520 The fetch handler is asked to retrieve a SINGLE record from a given
521 result set (the front-end server will automatically call the fetch
522 handler as many times as required).
524 The parameters exchanged between the server and the fetch handler are
527 ## Client/server request:
529 HANDLE => ref ## Reference to data structure
530 SETNAME => "id" ## ID of the requested result set
531 OFFSET => nnn ## Record offset number
532 REQ_FORM => "n.m.k.l"## Client requested format OID
533 COMP => "xyz" ## Formatting instructions
537 RECORD => "" ## Record string
538 BASENAME => "" ## Origin of returned record
539 LAST => 0 ## Last record in set?
540 ERR_CODE => 0 ## Error code
541 ERR_STR => "" ## Error string
542 SUR_FLAG => 0 ## Surrogate diagnostic flag
543 REP_FORM => "n.m.k.l"## Provided format OID
546 The REP_FORM value has by default the REQ_FORM value but can be set to
547 something different if the handler desires. The BASENAME value should
548 contain the name of the database from where the returned record originates.
549 The ERR_CODE and ERR_STR works the same way they do in the search
550 handler. If there is an error condition, the SUR_FLAG is used to
551 indicate whether the error condition pertains to the record currently
552 being retrieved, or whether it pertains to the operation as a whole
553 (eg. the client has specified a result set which does not exist.)
555 If you need to return USMARC records, you might want to have a look at
556 the MARC module on CPAN, if you don't already have a way of generating
559 NOTE: The record offset is 1-indexed - 1 is the offset of the first
564 A full featured Z39.50 server should support scan (or in some literature
565 browse). The client specifies a starting term of the scan, and the server
566 should return an ordered list of specified length consisting of terms
567 actually occurring in the data base. Each of these terms should be close
568 to or equal to the term originally specified. The quality of scan compared
569 to simple search is a guarantee of hits. It is simply like browsing through
570 an index of a book, you always find something! The parameters exchanged are
575 HANDLE => $ref ## Reference to data structure
576 TERM => 'start', ## The start term
577 NUMBER => xx, ## Number of requested terms
578 POS => yy, ## Position of starting point
579 ## within returned list
580 STEP => 0, ## Step size
584 ERR_CODE => 0, ## Error code
585 ERR_STR => '', ## Diagnostic message
586 NUMBER => zz, ## Number of returned terms
587 STATUS => $status, ## ScanSuccess/ScanFailure
588 ENTRIES => $entries ## Referenced list of terms
591 where the term list is returned by reference in the scalar $entries, which
592 should point at a data structure of this kind,
598 { TERM => 'energy density',
601 { TERM => 'energy flow',
609 The $status flag should be assigned one of two values:
611 Net::Z3950::SimpleServer::ScanSuccess On success (default)
612 Net::Z3950::SimpleServer::ScanPartial Less terms returned than requested
614 The STEP member contains the requested number of entries in the term-list
615 between two adjacent entries in the response.
619 The argument hash recieved by the close handler has one element only:
623 HANDLE => ref ## Reference to data structure
626 What ever data structure the HANDLE value points at goes out of scope
627 after this call. If you need to close down a connection to your server
628 or something similar, this is the place to do it.
630 =head2 Support for SRU and SRW
632 Since release 1.0, SimpleServer includes support for serving the SRU
633 and SRW protocols as well as Z39.50. These ``web-friendly'' protocols
634 enable similar functionality to that of Z39.50, but by means of rich
635 URLs in the case of SRU, and a SOAP-based web-service in the case of
636 SRW. These protocols are described at
637 http://www.loc.gov/sru
639 In order to serve these protocols from a SimpleServer-based
640 application, it is necessary to launch the application with a YAZ
641 Generic Frontend Server (GFS) configuration file, which can be
642 specified using the command-line argument C<-f> I<filename>. A
643 minimal configuration file looks like this:
647 <cql2rpn>pqf.properties</cql2rpn>
651 This file specifies only that C<pqf.properties> should be used to
652 translate the CQL queries of SRU and SRW into corresponding Z39.50
653 Type-1 queries. For more information about YAZ GFS configuration,
654 including how to specify an Explain record, see the I<Virtual Hosts>
655 section of the YAZ manual at
656 http://indexdata.com/yaz/doc/server.vhosts.tkl
658 The mapping of CQL queries into Z39.50 Type-1 queries is specified by
659 a file that indicates which BIB-1 attributes should be generated for
660 each CQL index, relation, modifiers, etc. A typical section of this
661 file looks like this:
664 index.dc.subject = 1=21
665 index.dc.creator = 1=1003
669 This file specifies the BIB-1 access points (type=1) for the Dublin
670 Core indexes C<title>, C<subject> and C<creator>, and the BIB-1
671 relations (type=2) corresponding to the CQL relations C<E<lt>> and
672 C<E<lt>=>. For more information about the format of this file, see
673 the I<CQL> section of the YAZ manual at
674 http://indexdata.com/yaz/doc/tools.tkl#tools.cql
676 The YAZ distribution include a sample CQL-to-PQF mapping configuration
677 file called C<pqf.properties>; this is sufficient for many
678 applications, and a good base to work from for most others.
680 If a SimpleServer-based application is run without this SRU-specific
681 configuration, it can still serve SRU; however, CQL queries will not
682 be translated, but passed straight through to the search-handler
683 function, as the C<CQL> member of the parameters hash. It is then the
684 responsibility of the back-end application to parse and handle the CQL
685 query, which is most easily done using Ed Summers' fine C<CQL::Parser>
686 module, available from CPAN at
687 http://search.cpan.org/~esummers/CQL-Parser/
691 Anders Sønderberg (sondberg@indexdata.dk),
692 Sebastian Hammer (quinn@indexdata.dk),
693 Mike Taylor (indexdata.com).
697 Any Perl module which is useful for accessing the database of your